[Fix]: Restrict mode + warnings and errors in logs

[jdurand-teclib]

• I have performed a self-review of my code.
• I have updated the CHANGELOG with a short functional description of the fix or new feature.
• This change requires a documentation update.

Description

• It fixes a bug where restrict mode was broken
• Here is a brief description of what this PR does
  • Remove deprecated usage of front/category.php and front/category.form.php
  • Remove variable assignation by reference in hook.php
  • Fix restrict mode broken because of:
    • A missing alias in a SQL request that was later silently making PHP refer to an unknown index in an array
    • A missing filtering in a SQL request that was supposed to filter group according to strict mode enablement